Could the greenest car be the one you are driving now? Well, that depends on which green you are talking about (Mother Nature or money), and the particular cars. Here are some factors to consider when you are grappling with buying “used” or “new.”

SmartWay guidance: Fortunately, the EPA’s SmartWay program goes back to 2000, so you can use it as your guide even if you are buying a used car.

Price: Depending on the vehicle, there could be a huge price discrepancy between a new car versus a late-model used car. However, it is important to consider federal and state incentives (especially if you’re in the market for an EV or PHEV, since these cars may be eligible for incentives), and more favorable financing terms that are available for newer-model vehicles.

Environmental concerns: Significant advances have been made in recent years regarding fuel efficiency and emissions controls in SmartWay-certified vehicles. For example, four years ago, the minimum gas mileage for a SmartWay-certified new gasoline model was 20 mpg; for 2013 models, it is 26 mpg.

Maintenance: A vehicle’s maintenance costs generally increase with age. Costly maintenance expenses may be hedged by purchasing a certified pre-owned vehicle or an extended warranty.

Insurance: Insuring a used car is usually less expensive than insuring a new one because the vehicle’s value is less. However, if the new vehicle has significant safety advantages over the used vehicle, then you could actually pay a lower premium.